How to Break and Shake Grain Jars

Break and shake grain jars

Share This Post

For fungi enthusiasts and aspiring mycologists, one of the most exciting activities is growing mushrooms at home. Among the techniques in this endeavor, a simple yet vital step is often underestimated: the break and shake process of grain jars. While it might seem like a small detail, it is actually a key practice that can significantly impact your mushrooms’ growth and overall yield. Let’s delve into why this process is important and how it contributes to successful home-based mushroom cultivation.

Understanding the Mushroom Life Cycle

Mushrooms begin their life as spores, which, under the right conditions, will germinate and grow into a thin network of cells called mycelium. Mycelium is essentially the vegetative part of a fungus, and it acts as the mushroom’s root system, drawing nutrients from the substrate it’s grown in, which often consists of a mix of grains.

When you’re growing mushrooms in jars, the grains serve as the substrate. After the spores have been introduced into the jar and conditions are just right, they’ll germinate, spreading the mycelium throughout the substrate. The mycelium will eventually consolidate and create fruiting bodies, the actual mushrooms, that will emerge from the substrate. This is where breaking and shaking come in.

The Role of the Break and Shake

So why break and shake your grain jars?

  1. Promotes Even Mycelium Distribution: Breaking and shaking your jars effectively redistributes the mycelium, ensuring that it spreads evenly throughout the jar. This leads to a uniform colonization of your substrate, helping it to mature more quickly and efficiently.
  2. Boosts Growth Rates: By distributing the mycelium, you are giving the faster-growing sections the chance to colonize grain that may be lagging behind. Essentially, breaking and shaking stimulate the mycelium to re-establish itself, sparking a new wave of growth. This technique can significantly speed up colonization times.
  3. Detects Contamination Early: Contaminants are a constant concern in mushroom cultivation. By breaking and shaking your jars, you give yourself an opportunity to identify any signs of contamination. This can include an unusual color, smell, or a slowdown in the colonization process. Early detection means you can isolate and remove contaminated jars, protecting the rest of your operation.
  4. Encourages Strong Mycelium Networks: Breaking and shaking the grain jars cause a degree of stress to the mycelium, which may seem counterintuitive. However, just as muscles strengthen when stressed, so too does mycelium. The process forces the mycelium to recover and regrow, resulting in a more robust and resilient mycelium network.

Break and Shake

Timing is crucial when it comes to breaking and shaking your grain jars in mushroom cultivation. The process is typically carried out when the mycelium has colonized around 20-30% of the jar. However, there’s some variability depending on the strain of mushroom and the specific conditions of your setup.

Let’s explore some of the key factors to consider when determining when to break and shake your grain jars:

  1. Mycelium Colonization: Look for mycelium colonization signs to reach about 20-30% of the jar. The mycelium will appear as a fluffy white substance growing over the grains. At this point, the mycelium has a strong hold on the grains and won’t be easily damaged by shaking.
  2. Substrate Condition: Ensure the grains aren’t overly moist or dry. Too much moisture can create a breeding ground for bacteria, while too little moisture may lead to slow or incomplete colonization.
  3. Visible Contamination: If you notice any strange colors or smells coming from the jar before the 20-30% colonization mark, it may be necessary to break and shake early to help confirm a possible contamination. Remember, this is a preventive step and it’s best to remove any contaminated jars immediately to avoid spread.
  4. Variation in Growth Rates: If you notice some areas of the jar are colonizing much faster than others, it could be beneficial to break and shake earlier to evenly distribute the mycelium.

After shaking, allow the jars to sit undisturbed until full colonization occurs, which can take anywhere from a few days to a couple of weeks, depending on the strain and environmental conditions.

When not to Break and Shake

The following image shows a grain jar that has colonized too much. Breaking and shaking the grain jar at this point would actually slow down the colonization process as the mycelium would have to re-form its connections. The best time to break and shake your grain jars is when you see about 30% colonization.

Break and Shake bad example


The art of mushroom cultivation requires patience, care, and attention to detail. While the act of breaking and shaking your grain jars might seem simple or even brutal, it is a crucial technique for encouraging vigorous growth and a successful yield. By evenly distributing mycelium, promoting growth, facilitating early detection of contamination, and fostering strong mycelial networks, this technique proves itself to be indispensable for both novice and experienced growers.

Remember, as you delve deeper into the fascinating world of mycology, every small step and technique matters in the grand scheme of cultivation. Therefore, the next time you find yourself questioning whether breaking and shaking your grain jars is necessary, consider the vital role it plays in cultivating a successful and bountiful mushroom harvest.

Subscribe To Our Newsletter

Get updates and learn from the best

More To Explore

Do You Want To Learn More?

drop us a line and keep in touch